Pressure equalizer



Patented May 19, 1953 PRESSURE EQUALIZER Emmett Lee Alexander, Enid, kla., assignor to The George E. Failing Supply Company, Enid, 0kla., a corporation of Oklahoma Application April 10, 1948, Serial No. 20,265

3 Claims. Cl. 13830) This invention relates to a pressure equalizer for use in the discharge line of a high pressure pump, for example, a mud pump used in circulatin drilling fluid during the rotary drilling of a well and has for its principal object to provide an equalizer of this character that smooths out pulsations or surges in the drilling fluid and which reduces or eliminates hammer and line shocks.

Previously the discharge of such pumps were provided with a pneumatic pressure accumulator chamber or dome in which entrapped air acted to cushion pressure pulsations and destructive shocks caused by liquid surges in the discharge line but when such a device is effective at low pressures it is not effective when the pressure is increased for the reason that when the entrapped air is compressed it does not give the desired cushion. This difficulty is overcome in part by equipping the surge chamber with an inflatable bladder that can be preloaded with compressed air at any desired pressure. Therefore, the mud or liquid enters the surge chamber at or above the preloaded pressure and the pressure surges compress the bladder in such a way that the pressure therein is always equal to the line pressures. However, with this arrangement reduction of pump pressure below the preloaded pressure of the bladder again results in pulsations and surge knocks because of the preloaded pressure maintained in the bladder. It is, therefore, a further object of the present invention to provide an equalizer that is substantially uniformly eifective throughout the pressure range of such pumps.

In accomplishing these and other objects of the invention as hereinafter pointed out, I have provided improved structure, the preferred form of which is illustrated in the accompanying drawing wherein:

Fig. 1 is an elevation, partly in section, of an equalizer embodying the features of the present invention and showing one of the bladders functioning under low pressure.

Fig. 2 is a similar view showing function of the bladders under high pressures.

Fig. 3 is a cross section on the line 3-3 of Fig. 1.

Fig. 4 is an elevational view partly in section of another form of equalizer embodying the features of the present invention.

Referring more in detail to the drawings:

l designates a pressure equalizer embodying the features of the present invention and which includes a casin comprising an elongated cylinder 2 provided at the ends with annular flanges 3 and 4 for attaching heads 5 and 6. The heads '5 and 6 each include a dome portion 1 substantially conforming to thediameterof the cylinder 2 and an annular flange portion 8 which seats upon the flanges 3 and 4 for attachment by fastening devices such as cap screws 9 that extend through suitable openings ID in the flanges 8 and into internally threaded openings H of the flanges 3 and 4. Inset within the respective ends of thecylinder'2 are seating rings l2 and [3' that are spaced apart to provide a fluid receiving chamber [4 therebetween. The members l2 and I3 are of circular formation and are provided with concave recesses I5 facing the concaved sides of the dome-shaped heads to provide bladder chambers I5 and II which connect with the chamber l4 through ports 18 and IS in the respective seat members. The ports I! and l8'are preferably covered by grids or perforate plates 20 and 21 having a plurality of apertures 22 through which pressure liquid in the chamber I3 enters the bladder chamber. The grids are preferably of circular formation and are seated within annular shoulders 23 encircling the openings I? and 8 as shown in Fig. 1-.

Mounted in the bladder chambers are bladders 24 and 25 formed of resilient material such as rubber and having an annular wall 25 and preferably curved end walls 21 and 28 correspondin to the curvature in the ends of the compartments. The heads 5 and 6 are each provided with a valve 29 such as ordinarily employed in the inner tube of an automobile and which in cludes a threaded stem 30 adapted to project through an opening 3| in the heads and secured by a nut 32. The outer ends of the stems may be closed by the usual dust caps 33. The interior of the stems are provided with cores equipped with valving members (not shown) to retain pressure in the respective bladders. Opposite diametrical sides of the cylinder are provided with bosses 34 and 35 having internally threaded openings 36 and 37 for admission of pressure fluid such as the drilling fluid discharged from a mud pump. The equalizer may be mounted on the discharge header of the pump or flow line 38 through which the fluid under pressure is delivered to the drill pipe. When connected with the line 38 the line may be provided with a T fitting 39 and the branch 40 thereof is provided with a nipple 4| that screws within one of the openings 36 or 31 to mount the cylinder.

In the illustrated instance the opposite opening is closed by a plug 42. If desired one section of the flow line may beconnected into the opening 36 and the other section into the opening 31 so that the flow is directly through the pressure chamber.

The form of the invention shown in Fig. 4 consists of a pair of cylinders 43 and 44 each having a cylindrical wall 45 and a'swaged end 46 merging into a branch '4! at each end of a T- vshaped manifold 48. The branch 49 of the manifold is mounted in the pressure flow line. The opposite ends of the cylinders are retained in spaced relation by a plate 50 which projects laterally from the peripheries of the walls 45 to provide a flangefor'attaching'a 'headplate 5| by means of fastening "devices 52 similar to the fastening devices described. The head plate 49 is provided with dome portions 53 and 54 for closing the open ends of the cylinder compartments and provide abutments for the bladder-5'55 and 56 which are of similar construction as the. bladders previously described. The bladdersareretained from blocking inlets to the manifold by means of grid plates 51 and .58 which have.

openings 59 therein to pass the fluid into the bladder compartments.

In using an equalizer constructed and assem- -b1edasillustratedin Figs..l, 2, andB-thebladders are charged with compressed air orother com-- pressed fluid. to any desired pressure depending upon the range of operating pressures of the pumpwith which.theequalizerisused. The bladders..may be inflated by connecting an air hose with. the stems of the bladder valves' and admitting pressure until .the pressure contained there- .in correspondswith the operating vpressurerange of the pump. For example, where the operating range. is from, 35 to 125. pounds. one of the bladdersmay be inflated to apressure of 25 pounds and the other 51) pounds. Therefore, when the pump is operating at 35. pounds discharge .pressure the bladder having the 50 pound internal .pressure is .notaffected by the pump .pressure but the bladder having the 25.--pound pressure will be compressed until the air therein is substantially equal to the .35-pound discharge pressure. When the pump pressure .is. below 50 pounds, pulsations will be smoothed out incidental to compression. and expansion-of theair. in-the cylinder having the 25 pound pressure. When the pressure .rises above'50 pounds the other bladder will. begin to function and take up. where the bladder having lower pressure is inefiicient to maintain the --desired equalizing action on the drilling fluid.

The form of invention illustrated in Fig. 4- operatesfin the same manner with the-exception that thepressure acts throughthe manifold 56 andthrough the .gridson the respective bladders.

When in use the equalizers need little attention other than an occasional check on the bladder air pressure. If a bladder fails to maintain operating air pressure it is readily removed and replaced with a new bladder by removing the valve core to permit exhaustingof air fromthe bladder, after which the cap screws areremoved so that the head'may be lifted from its enclose :pressure chambers from said passage, and a deformable gas filled bladder in each chamber and having portions normally seated on said grids and both of said-bladders being simultaneously ing cylinder'to permit removal of the bladder.

The'bladder may "then be readily detachedupon removal of the jambnut 31. A new bladder may then be appliedto the head and secured by the 'jamb nut, after which'the projecting endis projected into the open'end ofthe cylinder to permit seating of the headwhich is again attached by the cap=screws 9. The bladder is then inflated with the desired pressure and the operation rerange of arpumpcand pressure line with which 7 itis; associated.

What I claimanddesira to secure by Letters .Ratentis:

:1'. Asurgeequalizer forr-a iiow=duct containing subject toth'esame pressures in the flow duct, one of-said bladders containing a pressure corresponding to the lower portion of the pressure range and the other containing a pressure corresponding with the upper portion of the pressure range whereby the member having the lower pressure responds tothe lower pressure insaid flow duct and the member having the higher pressure responds to the higher pressure in equalizing pulsations in said pressure flow.

2. A surge equalizer for afiow .duct containing liquid-under pulsating flow through'awidely variable pressure range including a casing having separate pressure chambers in opposed coaxial relation, said casing having connection with the "flow :duct at a point intermediate the pressure chambers, grids spaced apart within the casing and providing a space between the pressure chambers in connection with said passage, and a deformable .gas filled bladder .in each chamber and having portions normally seated on said grids and both of said bladders being simultaneously subject to the same pressures in the *fiow:duct,;one of said bladders-containing a pressure corresponding to the lower portion of the pressure range :andtthe'other containing apressure corresponding with-theupper portion of the pressure range whereby the member having the lower pressureresponds to the lower pressure in said flow. duct jand the member having the higher pressure responds to the higher pressure in equalizing pulsations in. said pressure. flow.

3. A-surge equalizer for a.- flow duct containing liquid under pulsating. flowv through a widely variable-pressure; range including-a casing having laterally spaced parallel pressure chambers,,-a manifold connecting said pressure chambers and providing a.pressure.transmission passage con.- nected with the fiow-cluctpgrids separating-the pressure chambers-from said passage, and. a. deformable gas filled bladder in. each chamber and having portions normallyseated on. said grids-and both subject -to the same pressures inv the fiovv duct, oneof said bladders containing 'a-pressure corresponding to the lower portion of the pressure range and the 'other containingsa pressure corresponding with theupper portion of. the-pressure rangewherebythe member having thelower pressure responds to the lower pressure in said flow duct. and the. member. having the higher-pressure responds to the higher pressure in equalizing pulsations insaidpressurefiow- EMMETT 'References "Cited in the file of this patent UNITED -STATES. PATENTS :Number Name Date 8512;150 -Whitney Apr. 30, 1 907 125383.180 FEllinwo'o'd Aug. 21, 1945 2,389,792 .Lippincott Nov. '27, 1 945 2.446.358 Yates et al. Aug. 3, I948 2;4=714,554 Stephens et. al. June 28, 1949 -2, 5"4=0,-6'76 Johnson. 'etxal. Feb. 6; 1951 

